The invention relates to a magnetic rotary coupling with an inner coupling member on which an inner magnetic device is located with an axis of magnetic symmetry transverse to the axis of rotation. The magnetic device comprises two pairs of magnetic poles, each pair defining a magnetic axis between them that is aligned at an angle to a radius from the axis of the coupling. The coupling also includes an outer coupling member on which a respective outer magnetic device is located symmetrically with respect to the inner magnetic device, the magnetic poles of the outer magnetic device being adjacent to those of the inner magnetic device and being aligned at an angle of about 30.degree. to the axis of magnetic symmetry of the inner magnetic device.
In a known magnetic central rotary coupling (O. Richter, R. V. Voss, "Bauelemente der Feinmechanik" [Structural Elements of Precision Mechanics], 8th Edition, Verlag Technik, Berlin 1959, p. 330), the magnetic devices on the outer coupling member consist of a permanent magnet in the form of a circular segment, and the magnetic field lines of these permanent magnets emerge at the poles formed by pole pieces of these permanent magnets which project toward the inner coupling member. A magnetic device on the inner coupling member contains only one permanent magnet which is magnetized in the direction perpendicular to the axis of rotation and has pole pieces which are branched at their ends and each form a pair of magnetic poles. These magnetic poles are aligned at an angle to a radius from the axis of rotation of the magnetic device and are arranged symmetrically on both sides of this radius.
It is a disadvantage of this known central rotary coupling that the magnetic devices must contain relatively large and expensive permanent magnets, which of necessity also have considerable weight, to ensure that a sufficiently large torque can be transmitted. This leads to friction loss in the bearings of the rotary couplings. The fabrication of circular-segment permanent magnets of the outer magnetic devices with separate pole pieces, as well as the fabrication of the branch pole pieces of the inner magnetic device also increase the manufacturing costs.